package cn.wawi.common.filter;

import java.util.HashSet;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@SuppressWarnings("unchecked")
public class WebSessionListener implements HttpSessionListener{
	
	private Logger log=LoggerFactory.getLogger(WebSessionListener.class);
	
	public void sessionCreated(HttpSessionEvent event) {
		HttpSession session = event.getSession();
		ServletContext application = session.getServletContext();

		// 在application范围由一个HashSet集保存所有的session
		HashSet<HttpSession> sessions = (HashSet<HttpSession>) application.getAttribute("sessions");
		if (sessions == null) {
			sessions = new HashSet<HttpSession>();
			application.setAttribute("sessions", sessions);
		}

		// 新创建的session均添加到HashSet集中
		sessions.add(session);
		log.info("session："+session.getId()+" add");
		// 可以在别处从application范围中取出sessions集合
		// 然后使用sessions.size()获取当前活动的session数，即为“在线人数”
	}

	public void sessionDestroyed(HttpSessionEvent event) {
		HttpSession session = event.getSession();
		ServletContext application = session.getServletContext();
		HashSet<HttpSession> sessions = (HashSet<HttpSession>) application.getAttribute("sessions");

		// 销毁的session均从HashSet集中移除
		sessions.remove(session);
	}

}
